Tile Calculator: How Many Tiles, Boxes and Grout?
Enter the area, tile size, grout joint width and tiles per box. You get the tile count with waste, the boxes to buy and how much grout fills the joints. After switching units, re-enter your measurements.
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Formula
cell = (tile length + joint) × (tile width + joint)
tiles = round up (area ÷ cell × (1 + waste%))
boxes = round up (tiles ÷ tiles per box)
grout (L) = area ÷ cell × (cell − tile length × tile width) × thickness × (1 + waste%) × 1000
Worked example
A 10 ft by 10 ft floor (9.2903 m²), 12 in square tiles, 3 mm joint, 8 mm thick, 10% waste, 10 tiles per box:
- Cell: (0.3048 + 0.003)² = 0.094741 m². Tiles before waste: 9.2903 ÷ 0.094741 = 98.06.
- With waste: 98.06 × 1.1 = 107.9, so 108 tiles, which is 11 boxes.
- Grout: 98.06 × (0.094741 − 0.092903) × 0.008 m = 0.00144 m³ = 1.44 L, plus 10% = 1.59 L, about 2.54 kg.
Assumptions
- The grout joint is entered in millimetres in both unit systems; 3 mm is about 1/8 inch.
- Tiles are laid in a straight grid. Grout volume ignores the extra needed for uneven floors, rounded edges and cleaning.
- Mixed cement grout weighs about 1.6 kg per litre; epoxy and pre-mixed grouts differ.
- Cuts and breakage are covered by the waste percentage; boxes are always rounded up.
Frequently asked questions
How many 12 inch tiles do I need for 100 square feet?
With a 3 mm (1/8 in) joint each tile takes up 12.12 × 12.12 in, so 100 sq ft needs about 98 tiles. Adding 10% for cuts gives 108 tiles, which is 11 boxes of 10.
How much waste should I allow for tiles?
Allow 10% for straight layouts and about 15% for diagonal, herringbone or small rooms with many cuts. A few spare tiles from the same batch are also useful for later repairs.
How is the grout amount estimated?
The calculator finds the volume of each joint (the space around every tile times the tile thickness), multiplies by the number of tiles and adds your waste percentage. For 100 sq ft of 12 in tiles with 3 mm joints and 8 mm tiles that is about 1.6 litres, or 2.5 kg at 1.6 kg per litre. Treat it as a minimum, since uneven floors and deep joints use more.
Does grout joint width change how many tiles I need?
Slightly. Wider joints make each tile cover more area, so you need fewer tiles but more grout. A 10 mm joint on 12 in tiles lowers the count to about 94 before waste against 98 at 3 mm, but grout rises several times over.